Tuning fork resonator element and tuning fork resonator

ABSTRACT

A tuning fork resonator element that has a base portion, first and second resonating arms extending from the base portion in a first direction, and a support frame sandwiching the first and second resonating arms and being connected to the base portion includes: a first excitation electrode, formed in an area close to a connection portion with the base portion of the support frame, being connected to a mount electrode with a conductive adhesive; a second excitation electrode, formed in at least one of an area sandwiching the first and second resonating arms of the support frame and an area positioned farther than the first and second resonating arms in the first direction, being connected to a mount electrode with the conductive adhesive; and a cut portion of the support frame formed on an external surface of the support frame.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a tuning fork resonator element and atuning fork resonator using a piezoelectric material.

2. Related Art

A tuning fork resonator element is manufactured by forming a tuning forktype shape from a piezoelectric substrate and an electrode on the frontsurface, utilizing a photolithography technique.

In particular, formation methods of electrodes and support methods fortuning fork resonator elements have recently been studied for thepurposes of improvements in performance and productivity of thinner andminiaturized tuning fork resonator elements.

A first example of related art, JP-A-2006-339729, describes that inorder to improve the accuracy of light exposure for a crotch portion ofa tuning fork, a mask is brought into contact with a resist formed on anelectrode formation surface of a tuning fork resonator element and alight source is inclined at a predetermined angle so that light appliedto an inclined surface of a crotch portion formed between resonatingarms is made closer to the direction of applying the lightperpendicularly to the inclined surface, thus performing light exposure.

Also, a mount structure where a support arm is joined to and supportedwith a base is disclosed.

In a second example of related art, JP-A-2001-156584, it is disclosedthat side end surfaces of a piezoelectric element chip are formed to beoutwardly convex such that inclined surfaces having slopes of 5 to 20degrees with respect to a direction perpendicular to the upper surfaceor the lower surface intersect with each other in the center portion inthe thickness direction from the upper surface and the lower surface.

It is also disclosed that in forming a resist for forming electrodes forthis purpose, applying ultraviolet light from right above or at an angleof 0 to 30 degrees enables the resist on the side end surfaces to beexposed to light with reliability.

Thus, it is disclosed that electrodes can be accurately formed in sideend surfaces, particularly in the crotch portion.

This eliminates a short-circuit between electrodes, thus preventingdefective products.

It is also disclosed that the amount of polishing is controlled byjetting a solid-gas two-phase jetting flow from a jetting opening of anozzle to cause side end surfaces of a piezoelectric element chip to beinclined.

A third example of related art, JP-A-54-151391, describes that the sizeof an etching residue in the crotch portion of a tuning fork is relevantto the space and thickness of the resonating arm.

A fourth example of related art, JP-A-2006-311088, discloses that twosupporting arms are each joined to two points of electrode portions of asubstrate through a conductive adhesive.

In the first related art example, as shown in FIG. 9, a tuning forkresonator element has a structure in which two support arms 91 areprovided at positions sandwiching two resonating arms 11 and the supportarms 91 are each mounted on a base through a conductive adhesive 92.

With such a structure, a portion that is likely to function as a leakagepath is the crotch portion of the resonating arm.

Therefore, as disclosed in the third related art example, an etchingresidue in the crotch portion of a resonating arm is formed using thespace and thickness of the resonating arm, allowing a resist of thecrotch portion to be exposed to light if the exposure is perpendicularto the substrate to prevent a short-circuit between electrodes.

Alternatively, an etching residue in the crotch portion of a resonatingarm is formed by the adjustment of conditions such as etchantconcentration and etching time, allowing a short-circuit betweenelectrodes of the crotch portion to be prevented.

However, with a structure of the first related art example, if an impactis applied from the outside, leading ends of the resonating arms 11 andleading ends of a base portion are dramatically displaced up and downwith a mount portion serving as a fulcrum as shown in a side view inFIG. 10.

Therefore, a clearance between a resonator element and a package as wellas a clearance between a resonator element and a lid need to be large.

In the structure of the first related art example, however, if an impactfrom the outside is applied, the leading end of the resonating arm 11and the leading end of the base portion are largely displaced with themount portion serving as the fulcrum, as shown in the side view of FIG.10.

Therefore, a clearance between the resonator element and the package anda clearance between the resonator element and the lid need to be large.

If a structure of fixing a resonator element by using a conductiveadhesive at two points of each support arm as in the fourth related artexample is employed, it is difficult to provide a card-type tuning forkresonator needed to have a thickness of 0.4 mm or less so as to ensure aclearance between the resonator element and the package and a clearancebetween the resonator element and the lid.

The use of the inclined light exposure disclosed in the first relatedart example and a method of jetting a solid-gas two-phase jetting flowdisclosed in the second related art example degrades the throughput toincrease the manufacturing cost as well as productivity.

SUMMARY

The present invention can be achieved by the following.

A tuning fork resonator element according to a first aspect of theinvention has a base portion, first and second resonating arms extendingfrom the base portion in a first direction, and a support framesandwiching the first and second resonating arms and being connected tothe base portion.

The tuning fork resonator element includes a first excitation electrode,which is connected to a mount electrode with a conductive adhesive,formed in an area close to a connection portion with the base portion ofthe support frame, a second excitation electrode, which is connected toa mount electrode with the conductive adhesive, formed in at least oneof an area sandwiching the first and second resonating arms of thesupport frame and an area positioned farther than the first and secondresonating arms in the first direction, and a cut portion of the supportframe formed on an external surface of the support frame.

With such a structure, due to the cut portion of the base portion,electrode films left on the side surfaces of the support frame and thebase portion can prevent the first excitation electrode and the secondexcitation electrode from generating a short circuit.

The cut portion of the support frame can be formed in a process offorming the outline of the tuning fork resonator element, and thereforeelectrode films left on the side surfaces of the support frame and thebase portion can prevent a short circuit between the first excitationelectrode and the second excitation electrode without increasing thenumber of processes.

In the tuning fork resonator element according to the first aspect ofthe invention, the first and second excitation electrodes may each haveelectrode films on a front surface and a back surface of the supportframe and an electrode film on a side surface of the support frame forconnecting the electrode films on the front surface and the backsurface.

The electrode film on the side surface of the support frame may be cutin the cut portion of the support frame.

In the tuning fork resonator element according to the first aspect ofthe invention, it is preferable that a cut portion of the base portionbe formed on both sides in a width direction of the base portion, thefirst and second excitation electrodes each extend through electrodefilms on a front surface and a back surface of the base portion to theresonating arm, and the electrode films on the front surface and theback surface of the base portion be connected through an electrode filmof a side surface of the base portion and the electrode film on the sidesurface of the base portion be cut in the cut portion of the baseportion.

In the tuning fork resonator element according to the first aspect ofthe invention, it is preferable that a cut portion of the base portionbe formed on both sides in a width direction of the base portion, thefirst and second excitation electrodes each extend through electrodefilms on a front surface and a back surface of the base portion to theresonating arm, and the electrode films on the front surface and theback surface of the base portion be connected through an electrode filmof a side surface of the base portion and the electrode film on the sidesurface of the base portion be cut in the cut portion of the baseportion.

In the tuning fork resonator element according to the first aspect ofthe invention, it is preferable that a fin made by anisotropic etchingbe formed in the cut portion of the base portion.

In the tuning fork resonator element according to the first aspect ofthe invention, it is preferable that a substrate of the tuning forkresonator element be formed of quartz crystal including crystal axeshaving an X axis, a Y axis and a Z axis, the first direction be adirection closest to a direction of the Y axis among the crystal axes,and the width direction be a direction closest to a ±X axis directionamong the crystal axes and a fin on a +X axis side be longer than a finon a −X axis side.

In the tuning fork resonator element according to the first aspect ofthe invention, it is preferable that a space between the first andsecond resonating arms be longer than a width of the cut portion of thebase portion.

In the tuning fork resonator element according to the first aspect ofthe invention, it is preferable that a groove, a groove electrode formedin the groove and a side surface electrode be formed in each of thefirst and second resonating arms, and each of the groove have a tie barformed therein.

A tuning fork resonator according to a second aspect of the inventionincludes: a tuning fork resonator element; a base having the mountelectrode formed thereon and having a seal hole; a package frame closingpart of the seal hole and being layered on the base; a sealing memberfor sealing the seal hole; and a lid for sealing the package frame. Thetuning fork resonator element includes: a base portion; first and secondresonating arms extending from the base portion in a first direction; asupport frame sandwiching the first and second resonating arms and beingconnected to the base portion, a first excitation electrode formed in anarea close to a connection portion with the base portion of the supportframe, the first excitation electrode being connected to a mountelectrode with a conductive adhesive; a second excitation electrodeformed in at least one of an area sandwiching the first and secondresonating arms of the support frame and an area positioned farther thanthe first and second resonating arms in the first direction, the secondexcitation electrode being connected to a mount electrode with theconductive adhesive; and a cut portion of the support frame formed on anexternal surface of the support frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a top view showing a tuning fork resonator element accordingto an embodiment.

FIG. 2 is a bottom view showing the tuning fork resonator elementaccording to the embodiment.

FIG. 3 is a sectional view of areas having grooves formed therein ofresonating arms of the tuning fork resonator element according to theembodiment.

FIG. 4 is a top view showing a tuning fork resonator in which the tuningfork resonator element according to the embodiment is housed.

FIG. 5 is a side view showing the tuning fork resonator in which thetuning fork resonator element according to the embodiment is housed.

FIG. 6 is a front view showing the tuning fork resonator in which thetuning fork resonator element according to the embodiment is housed.

FIG. 7 is a flow chart showing a process flow of the tuning forkresonator element according to the embodiment.

FIG. 8 is an explanatory view schematically showing a sectional shape ofa tuning fork resonator element according to the embodiment in eachprocess.

FIG. 9 is a top view showing a tuning fork resonator of related art.

FIG. 10 is a side view showing the tuning fork resonator of related art.

DESCRIPTION OF EXEMPLARY EMBODIMENT

An embodiment of the invention will be described below with reference tothe accompanying drawings.

Embodiment

FIG. 1 is a top view showing a tuning fork resonator element accordingto the present embodiment.

FIG. 2 is a bottom view showing the tuning fork resonator elementaccording to the embodiment.

The bottom view used herein shows the bottom surface seen from the top,and the bottom surface actually seen from the bottom is reversed fromright to left.

The lid side of a package in which a tuning fork resonator element ishoused is the top surface (front surface) and the base side of thepackage is the bottom surface (back surface).

Note that in FIGS. 1 and 2, a tuning fork resonator element 10 formedfrom a quartz crystal substrate that is cut from quartz crystal with theZ axis used as the normal is taken as an example.

However, the tuning fork resonator element 10 only have to be apiezoelectric material having a crystal orientation.

For example, lithium tantalite and lithium niobate may be used.

Structure of Tuning Fork Resonator Element

The tuning fork resonator element 10 includes a base portion 18, firstand second resonating arms 11 extending in the Y axis direction from thebase portion 18, and a support frame 28 connected in the −Y axisdirection from the base portion 18 and is formed of a single crystalplate of single quartz crystal.

Structure of Resonating Arm

The leading end portion of the resonating arm 11 is provided with aweight portion 12 that is made of a metal film and that controls thefrequency by controlling the mass.

The resonating arm 11 is provided with side surface electrodes 19 fromthe front surface to the side surfaces and is provided with grooves 14and 15 on the top surface and the bottom surface and electrode filmsformed so as to cover the grooves 14 and 15, that is, groove electrodes13.

The resonating arms 11 are excited such that when one vibrates in the +Xaxis direction, the other vibrates in the −X axis direction.

Part of the weight portion 12 on the bottom surface is removed by laserexposure during frequency control and then is adhered to the base.

The weight adhered to the base may come into contact with the resonatingarms 11 to block flexural vibrations of the resonating arms 11.

Therefore, an extra clearance between the weight adhered to the base andthe resonating arm 11 needs to be provided.

To address this issue, it is possible to further reduce the thickness ofthe package with a structure of providing the weight portion 12 only onthe top surface, not on the bottom surface.

To enhance the excitation efficiency, the grooves 14 and 15 are providedon the top surface and the bottom surface of the resonating arm 11, andelectrode films, that is, the groove electrodes 13 are provided so as tocover the grooves 14 and 15.

However, a vibration component perpendicular to a quartz crystalresonator element substrate (hereinafter, referred to as a“perpendicular vibration component”) becomes large due to the externalshape of the tuning fork resonator element 10, the anisotropy of etchingprocesses of making grooves, and the pattern displacement between thetop surface and the bottom surface of the tuning fork resonator element10.

This tendency becomes more remarkable when the width of the resonatingarm 11 is decreased as the tuning fork resonator is miniaturized,causing manufacture variations of the tuning fork resonator element 10.

In particular, wide manufacturing variations in peak temperature oftemperature-frequency characteristics, Δf/f (frequency variation) ofcharacteristics of drive level (DL), and ΔCI (crystal impedance (CI)value variation) have been found.

To suppress the manufacturing variations, a tie bar 16 is providedbetween the grooves 14 and 15 of the resonating arm 11.

The action of the tie bar 16 can enhance the rigidity of the resonatingarm 11 in an area with the grooves 14 and 15 to realize stablevibrations, allowing the reduction of manufacturing variations.

To improve the resistance to impact from the outside, the tie bar 16 canuse a structure in which impact tends to be transmitted to theresonating arm 11, e.g., a frame supporting structure.

As the countermeasure against the manufacturing variations, the groove15 is further provided with a reduced width portion 17.

Structure of Base Portion

The base portion 18 has the width greater than the total width of theresonating arms 11 and the connection portion and has reduced widthportions 21 and 22.

The reduced width portions 21 and 22 has the effect of making itdifficult for the vibration energy of the resonating arms 11 to betransmitted to the support frame 28, so-called an energy-trappingeffect, to reduce the CI value.

The reduced width portions 21 and 22 have the effect of making itdifficult for the impact from the outside to be transmitted to theresonating arms 11.

The base portion 18 is connected with the support frame 28, and theconnection portion or the base portion 18 itself has first cut portions(cut portions of the base portion) 23 and 24.

Formed on the top surface and bottom surface of the base portion 18 areelectrode films 35 in which a first excitation electrode 31 to bedescribed later extends to the resonating arms 11.

The electrode films 35 on the top surface and bottom surface of the baseportion 18 are connected with a side surface of the base portion 18.

Step S19 of C-C′ in FIG. 8 shows section C-C′ of FIG. 1 after electrodeAu Cr etching.

A first electrode film (Cr film, and the same is true hereinafter) 83and a second electrode film (Au film, and the same is true hereinafter)84 are left without being etched and connect the top surface and thebottom surface.

On the other hand, the first cut portions 23 and 24 of the base portion18 have patterns in which the electrode films 35 are cut on the sidesurfaces.

Accordingly, the electrode films 35 on the top surface and bottomsurface of the base portion 18 are cut.

Step S19 of B-B′ in FIG. 8 shows section B-B′ of FIG. 1 after theelectrode Au Cr etching.

The first electrode film 83 and the second electrode film 84 are cut onthe side surfaces, so that the top surface is separated from the bottomsurface.

The widths of the first cut portions 23 and 24 of the base portion 18are formed to be narrower than the space between the resonating arms 11.

Structure of Support Frame

In the connection portion on the −Y axis side of the base portion 18,the support frame 28 and the base portion 18 are connected.

Formed in an area close to the connection portion, that is, a supportshort side 30 is a first excitation electrode 31, which is electricallyand mechanically connected to a mount electrode 51 provided in a base 55with a conductive adhesive 50 interposed therebetween.

The conductive adhesive 50 may be applied to the mount electrode 51 attwo points of the first excitation electrode 31 or along the supportshort side 30.

This makes it easy for the tuning fork resonator element 10 to besupported in parallel to the base 55.

Regarding the support frame 28, formed in two areas sandwiching theresonating arms 11 or at a position apart from the leading edges of theresonating arms 11 in the Y axis direction is a second excitationelectrode 29, which is electrically and mechanically connected to themount electrode 51 provided in the base 55 with the conductive adhesive50 interposed therebetween.

The conductive adhesive 50 may be applied to the mount electrode 51 attwo points of the second excitation electrode 29 or along a circularconnection portion 37 with which two portions of the support frame 28extending in the Y axis direction on the outsides of the resonating arms11 are circularly connected in their leading ends.

This makes it easy for the tuning fork resonator element 10 to besupported in parallel to the base 55. In the support frame 28, secondcut portions (cut portions of the support frame) 25 and 26 are formed.

The widths of the second cut portions 25 and 26 of the base portion 18are formed to be narrower than the space between the resonating arms 11.

Step S19 of D-D′ in FIG. 8 shows section D-D′ of FIG. 1 after theelectrode Au Cr etching.

The first electrode film 83 and the second electrode film 84 are left onthe top surface so as to form a connect electrode 38 while being removedon the side surfaces and the bottom surface by etching.

No electrode film is provided on the bottom surface.

Similarly, step S19 of E-E′ in FIG. 8 shows section E-E′ of FIG. 1 afterthe electrode Au Cr etching.

The first electrode film 83 and the second electrode film 84 are removedon the top surface, bottom surface and side surface on the +X side byetching.

The first electrode film 83 and the second electrode film 84 are left onthe side surface on the −X side.

In addition, if the thickness of the package is made thinner, the base55 for mounting the support frame 28 is made thinner and high rigidityof the support frame 28 is needed so as to cover the rigidity of thebase 55.

In this case, the cut portions 25 and 26 are made closer to the supportshort side 30.

Alternatively, the connect electrode 38 extends in the Y axis direction,and the cut portions 25 and 26 are provided in an area close to theleading end on the +Y side of the connect electrode 38.

Further, to make a countermeasure against short-circuit defects moreeffective, the second cut portions 25 and 26 may be provided in twoportions, a portion close to the support short side 30 and a portionclose to the leading end on the +Y side of the connect electrode 38.

Alternating Voltage

FIG. 3 is a sectional view of an area having the grooves 14 or 15 formedtherein of the resonating arms 11 of the tuning fork resonator element10 shown in FIGS. 1 and 2.

The resonating arms 11 has the top and bottom surfaces (front and backsurfaces) 71 facing opposite to each other, and first and second sidesurfaces 72 and 73 connecting the top and bottom surfaces 71 on theirboth sides.

In the case where the tuning fork resonator element 10 is made of quartzcrystal, regarding the crystal orientation, the front and back surfaces71 have an orientation in the Z axis direction, the first side surface72 has an orientation in the +X axis direction, and the second sidesurface 73 has an orientation in the −X axis direction.

The first side surface 72 of one resonating arm 11 (on the left side inFIGS. 1 and 2) and the second side surface 73 of the other resonatingarm 11 (on the right side in FIGS. 1 and 2) are arranged in parallelfacing each other.

The first side surface 72 is formed into a mountain shape in which thethickness of the resonating arm 11 increases in directions toward thecenter.

The thickness of the resonating arms 11 is defined by the space betweenthe top and bottom surfaces 71.

An excitation electrode film is formed on the resonating arm 11.

The excitation electrode film may have a multilayer structure includinga Cr film serving as an underlying film having a thickness of 10 nm ormore and 30 nm or less and an Au film having a thickness of 20 nm ormore and 50 or less formed on the Cr film.

The Cr film has high adhesion to quartz crystal and the Au film isresistant to oxidizing because of its low electric resistance.

The excitation electrode film includes first and second side surfaceelectrode films 77 and 79 formed on the first and second side surfaces72 and 73, respectively, and first and second inner surface electrodefilms 46 and 48 formed on the first and second inner surfaces 75 and 76,respectively.

The excitation electrode film constitutes the groove electrode 13 andthe side surface electrode 19.

Groove electrodes 13 and the side surface electrode 19 are connected toan alternating-current power supply by cross-wiring to apply alternatingvoltage as drive voltage so that the groove electrode 13 of oneresonating arm 11 (left side in FIGS. 1 and 2) and the side surfaceelectrode 19 of the other resonating arm 14 (right side in FIGS. 1 and2) have the same potential (+potential in the example in FIG. 3) whilethe side surface electrode 19 of one resonating arm 11 and the grooveelectrode 13 of the other resonating arm 11 have the same potential(−potential in the example in FIG. 3).

The applied voltage generates electric fields as shown by the arrows inFIG. 3, which excite the resonating arms 11 such that they vibrate inopposite phases to each other (such that the leading end sides of theresonating arms 11 move close to and apart from each other), thusgenerating flexural vibrations.

The alternating voltage is controlled so that the resonating arms 11vibrate in the fundamental mode.

Separation of First Excitation Electrode from Second ExcitationElectrode

As shown in FIG. 2, the first excitation electrode 31 of the supportframe 28 is electrically and mechanically connected to the mountelectrode 51 formed on the base 55 through the conductive adhesive 50 onthe bottom surface of the tuning fork resonator element 10.

The electrode film is formed on the top surface as well as the bottomsurface of the support frame 28 using a mask pattern to cause a resiston the side surface of corner portions 32 and on the side surface on the−Y axis side to be left.

As a result, the first excitation electrode 31 on the top surface inFIG. 1 is connected with the first excitation electrode 31 on the bottomsurface in FIG. 2 through the electrode film on the side surface of thesupport frame 28, a voltage applied to the mount electrode 51 has thesame potential as those of the first excitation electrodes 31 on the topand bottom surfaces.

Further, the first excitation electrode 31 on the top surface isconnected to the groove electrode 13 of one resonating arm 11 (on theleft side in FIG. 1) and the side surface electrode 19 of the otherresonating arm 11 (on the right side in FIG. 1) through the firstelectrode film 35 on the top surface.

On the other hand, as shown in FIG. 2, the second excitation electrode29 of the support frame 28 is electrically and mechanically connected tothe mount electrode 51 formed on the base 55 through the conductiveadhesive 50 on the bottom surface of the tuning fork resonator element10.

The electrode film is formed on the top surface as well as the bottomsurface of the support frame 28 using a mask pattern to cause a resiston the side surface of corner portions 32, on the side surface on the ±Xaxis side and on the side surface on the +Y axis side to be left.

As a result, the second excitation electrode 29 on the top surface inFIG. 1 is connected with the second excitation electrode 29 on thebottom surface in FIG. 2 through the electrode film on the side surfaceof the support frame 28, a voltage applied to the mount electrode 51 hasthe same potential as those of the second excitation electrodes 29 onthe top and bottom surfaces.

Further, the second excitation electrode 29 on the top surface isconnected to the connect electrode 38 through the electrode film on theside surface of the support frame 28 and then is connected to the secondelectrode film of the base portion 18 to be connected to the sidesurface electrode 19 of one resonating arms 11 (on the left side inFIG. 1) and to the groove electrode of the other resonating arm 11 (onthe right side in FIG. 1).

The outline is formed such that the contours of the corner portions 32are made using a mask pattern having predetermined sides and curvedlines.

In this way, a taper of the section can be controlled by angles of theside surface in the case of anisotropy etching of a quartz crystalmaterial.

As a result, a redundant structure having less disconnections on the topand bottom surfaces can be achieved.

Further, the top and bottom surfaces are suitably connected through theelectrode film not only on the side surfaces of the corner portions 32but also on the inner and outer side surfaces of the support frame 28and on the side surface of the base portion 18, thus achieving theredundant structure having less disconnections on the top and bottomsurfaces.

Here, in the case of a structure without the first cut portion 24, thefirst electrode films 35 of the base portion 18 and the secondexcitation electrode 29 of the support frame 28 have generated shortcircuits on the inner side surfaces of the base portion 18 and thesupport frame 28 in some cases.

This is because if the taper of the section of quartz crystal isapproximately perpendicular, a resist is not sufficiently exposed tolight in the light exposure process for the side surface electrode to beleft.

To address this issue, the first cut portion 24 is provided in thepresent embodiment.

The circulation of an etchant is poor in the first cut portion 24, andtherefore the etching rate in the vertical direction can be reduced inthe outline etching of quartz crystal.

As a result, a section having a large etching residue, that is, asection having a long fin can be formed.

The section having a long fin ensures that a resist formed on the finwill be exposed to light, enabling short-circuit defects caused by theresidue of the side surface electrode film to be suppressed.

In the case of a structure without the second cut portion 26, the firstexcitation electrode 31 of the base portion 18 and the second excitationelectrode 29 of the support frame 28 have generated short circuits onthe outer side surfaces on the +X axis side of the support frame 28 insome cases.

This is also because the taper of the section of quartz crystal isapproximately perpendicular and a resist is not sufficiently exposed tolight, so that the side surface electrode is left.

To address this issue, the second cut portion 26 is provided in theembodiment.

The second cut portion 26 can have a section having a long fin as thefirst cut portion 24 does.

As a result, short-circuit defects caused by the residue of the sidesurface electrode film can be suppressed.

Similarly, the second cut portion 25 suppresses a short-circuitgenerated on the outer side surface on the −X axis side of the supportframe 28 by the first excitation electrode 31 and the second excitationelectrode 29.

The first cut portion 23 may be used for suppression of short-circuitdefects between excitation electrodes as the first cut portion 24 andsecond cut portions 25 and 26 do.

However, as shown by hatching in FIGS. 1 and 2, the periphery of thefirst cut portion 23 has the same potential as that of the secondexcitation electrode. In other words, suppression of short-circuitdefects is not necessary.

In the embodiment, the first cut portion 23 functions as a balancer tobalance the right and left of the first cut portion 24.

It is possible to change patterns between the right and left to use thefirst cut portion 23 for suppression of short-circuit defects and thefirst cut portion 24 as a balancer. However, the effect of suppressingshort-circuit defects is small.

As the sectional view taken along the line B-B′ in step S19 in FIG. 8shows a section along the line B-B′, the left side (−X axis side) of thesection is more perpendicular and has a shorter fin than the right side(+X axis side) of the section.

As a result, the resist may be not sufficiently exposed to light tocause the residue of the film.

Package Structure

FIG. 4 is a top view showing the tuning fork resonator 60 in which thetuning fork resonator element 10 according to the embodiment is housed,FIG. 5 is a side view showing the tuning fork resonator 60, and FIG. 6is a front view showing the tuning fork resonator 60.

Formed on the top surface of the base 55 made of ceramics are the mountelectrodes 51.

The conductive adhesive 50 is applied onto the electrodes 51, and thefirst excitation electrode 31 and the second excitation electrode 29 ofthe tuning fork resonator element 10 are electrically and mechanicallyconnected to the conductive adhesive 50.

The mount electrodes 51 pass on the side surface of the base 55 and isexposed on the base bottom surface to be connected to an oscillationcircuit (not shown).

A seal hole 56 is further formed in the base 55.

Regarding the base 55, metalizing (not shown) is applied the insidediameter of the seal hole to enhance the adhesion with a sealingmaterial 57 to be described later.

A package frame 52 for housing the tuning fork resonator element 10 islayered on the base 55 so as to close part of the seal hole 56.

Further, a lid 58 is sealed so as to close the top surface opening ofthe package frame 52.

The lid may be sealed by using a metal brazing material and may also besealed by seam sealing.

To ensure the sealing properties, an intermediate layer may be providedbetween the package frame 52 and the lid 58.

After the lid 58 and the package frame 52 are sealed, the tuning forkresonator 60 is turned upside down, and then the sealing material 57(e.g., a metal ball made of an AuGe alloy) is inserted into the sealhole 56 and heated in the vacuum to seal the seal hole 56.

Thus, the tuning fork resonator element 10 is vacuum-housed.

Note that it is found that this method provides a resonator having a lowCI value as compared to the case of performing a lid sealing process invacuum without the use of the seal hole 56.

It is considered that this is because gas generated in the lid sealingprocess decreases the degree of vacuum inside the package decreases.

Manufacturing Process of Tuning Fork Resonator Element

FIG. 7 is a flow chart showing a process flow of the tuning forkresonator element 10 according to the embodiment.

A wafer cut using the Z axis as the normal is cleaned (step S1) andsputtered in the order of Cr and Au (step S2).

Next, a resist is applied (step S3) and exposed to light (step S4) anddeveloped (step S5) along the outline pattern, and Au and Cr formed infilms in step S2 are etched (step S6).

Next, the resist applied in step S3 is removed (step S7) and a resist isapplied again (step S8).

The resist applied in step S8 is exposed to light (step S9) anddeveloped (step S10) in a pattern of etching a groove.

Next, the outline of quartz crystal is etched using Au and Cr etched instep S6 as a mask (step S11).

Next, Au and Cr are etched in a resist pattern formed by the groovelight exposure in step S9 (step S12), and subsequently the groove formof quartz crystal is etched (step S13), and cleaning is performed (stepS14).

Next, Au and Cu, which will be electrodes, are sputtered (step S15), anda resist is applied (step S16).

Next, after a resist is applied (step S16), the resist is exposed tolight (step S17) and developed (step S18) in a pattern of formingelectrodes, and Au and Cr are etched into electrode shapes (step S19).

Next, the resist applied in step S16 is removed (step S20), and a weightis attached (step S21) and the frequency is controlled (step S22) tocontrol the frequency to obtain a desired frequency.

FIG. 8 is a sectional view schematically showing the sectional shape ofthe tuning fork resonator element formed in the process shown in FIG. 7.

In the figure, reference numeral 82 denotes quartz crystal; 83, Cr; 84,Au; 85, a resist; and 86, a mask pattern.

Steps S14 to S19 in FIG. 8 correspond to states after steps S14 to S19in FIG. 7.

The A-A′ in FIG. 8 corresponds to sections along the line A-A of acrotch portion 27 of the resonating arms 11 of the tuning fork resonatorelement 10 in FIG. 1 when cut in the Y axis line.

The B-B′ in FIG. 8 corresponds to sections along the line B-B′ betweenthe first cut portions 23 and 24 in FIG. 1.

The C-C′ in FIG. 8 corresponds to sections along the line C-C′ in FIG.1.

The D-D′ and E-E′ in FIG. 8 correspond to sections along the lines D-D′and E-E′ of support arms in FIG. 1 respectively.

In the C-C section of an area without a cut in the base portion 18, theleft side (the −X axis side) of the section is approximatelyperpendicular.

The vicinity of the side surface is masked, and the electrode formed onthe side surface connects the top surface with the bottom surface of thefirst excitation electrode 31 and the top surface with the bottomsurface of the second excitation electrode 29.

On the other hand, in the B-B′ section in FIG. 8, a long fin is formedon the side surface on the right side (+X axis side).

Further, a mask pattern for exposing the fin to light is used.

As a result, the resist applied to the fin can be exposed to light withreliability, enabling the suppression of a short circuit on the top andbottom surfaces between the first electrode film 35 and the secondexcitation electrode 29.

The D-D′ section and the E-E′ section also utilize fins so as tosuppress short circuits between the first electrode film 35 (firstexcitation electrode 31) and the second electrode film 36 (secondexcitation electrode 29).

In addition, it is found that the side surfaces on the left sides (−Xaxis sides) of the B-B′ section, C-C′ section, D-D′ section and E-E′section are more perpendicular than the side surfaces on the right sides(+X axis sides) and the crotch portion 27 of the resonating arms 11.

Therefore, to suppress short-circuit defects on the −X axis side, it ispreferable the cut width be narrower than the space between theresonating arms 11.

As described above, according to the tuning fork resonator element 10 ofthe embodiment, due to the first cut portions 23 and 24 of the baseportion 18, the electrode film left on the side surfaces of the supportframe 28 and the base portion 18 enables the prevention of a shortcircuit between the first excitation electrode 31 and the secondexcitation electrode 29.

The first cut portions 23 and 24 can be formed in a process of formingthe outline of the tuning fork resonator element 10.

Therefore, the electrode film left on the side surfaces of the supportframe 28 and the base portion 18 can prevent a short circuit between thefirst excitation electrode 31 and the second excitation electrode 29without increasing the number of processes.

The entire disclosure of Japanese Patent Application Nos: 2007-143001,filed May 30, 2007 and 2007-143002 filed May 30, 2007 are expresslyincorporated by reference herein.

What is claimed is:
 1. A tuning fork resonator element having a baseportion, first and second resonating arms extending from the baseportion in a first direction along and substantially parallel to alongitudinal axis of each of the first and second resonating arms, and asupport frame sandwiching the first and second resonating arms and beingconnected to the base portion, the tuning fork resonator elementcomprising: a first excitation electrode formed in an area close to aconnection portion with the base portion and the support frame, thefirst excitation electrode being connected to a mount electrode with aconductive adhesive; a second excitation electrode formed in an areasandwiching the first and second resonating arms of the support frameand in an area positioned farther than the first and second resonatingarms in the first direction, the second excitation electrode beingconnected to a mount electrode with the conductive adhesive; a pair ofcut portions of the support frame formed on side surfaces of the supportframe that are opposite to surfaces of the support frame opposingrespective ones of the first and second resonating arms, the pair of cutportions being disposed along a length of the support frame between thebase portion and a distal end of the support frame; a cut portion of thebase portion formed on both sides of the base portion in a widthdirection of the base portion; and a fin made by anisotropic etching isformed in the cut portion of the base portion to disconnect the firstexcitation electrode and the second excitation electrode; wherein thefirst and second excitation electrodes each extend through electrodefilms on a front surface and a back surface of the base portion to theresonating arm; and wherein the electrode films on the front surface andthe back surface of the base portion are connected through an electrodefilm of a side surface of the base portion, the electrode film on theside surface of the base portion being cut in the cut portion of thebase portion.
 2. The tuning fork resonator element according to claim 1,wherein: a substrate of the tuning fork resonator element is formed ofquartz crystal including crystal axes having an X axis, a Y axis and a Zaxis; the first direction is a direction closest to a direction of the Yaxis among the crystal axes; and the width direction is a directionclosest to a ±X axis direction among the crystal axes and a fin on a +Xaxis side is longer than a fin on a −X axis side.
 3. The tuning forkresonator element according to claim 1, wherein a space between thefirst and second resonating arms is longer than a width of the cutportion of the base portion.
 4. The tuning fork resonator elementaccording to claim 1, wherein: a groove, a groove electrode formed inthe groove and a side surface electrode are formed in each of the firstand second resonating arms.
 5. A tuning fork resonator, comprising: atuning fork resonator element having a base portion, first and secondresonating arms extending from the base portion in a first directionalong and substantially parallel to a longitudinal axis of each of thefirst and second resonating arms, and a support frame sandwiching thefirst and second resonating arms and being connected to the baseportion, the tuning fork resonator element including: a first excitationelectrode formed in an area close to a connection portion with the baseportion and the support frame, the first excitation electrode beingconnected to a mount electrode with a conductive adhesive; a secondexcitation electrode formed in an area sandwiching the first and secondresonating arms of the support frame and in an area positioned fartherthan the first and second resonating arms in the first direction, thesecond excitation electrode being connected to a mount electrode withthe conductive adhesive; and a pair of cut portions of the support frameformed on side surfaces of the support frame that are opposite tosurfaces of the support frame opposing respective ones of the first andsecond resonating arms, the pair of cut portions being disposed along alength of the support frame between the base portion and a distal end ofthe support frame; a cut portion of the base portion formed on bothsides of the base portion in a width direction of the base portion; afin made by anisotropic etching is formed in the cut portion of the baseportion to disconnect the first excitation electrode and the secondexcitation electrode; a base having the mount electrode formed thereonand having a seal hole; a package frame closing part of the seal holeand being layered on the base; a sealing member for sealing the sealhole; and a lid for sealing the package frame; wherein the first andsecond excitation electrodes each extend through electrode films on afront surface and a back surface of the base portion to the resonatingarm; and wherein the electrode films on the front surface and the backsurface of the base portion are connected through an electrode film of aside surface of the base portion, the electrode film on the side surfaceof the base portion being cut in the cut portion of the base portion. 6.The tuning fork resonator according to claim 5, wherein: a substrate ofthe tuning fork resonator is formed of quartz crystal including crystalaxes having an X axis, a Y axis and a Z axis; the first direction is adirection closest to a direction of the Y axis among the crystal axes;the width direction is a direction closest to a ±X axis direction amongthe crystal axes and a fin on a +X axis side is longer than a fin on a−X axis side.
 7. The tuning fork resonator according to claim 5, whereina space between the first and second resonating arms is longer than awidth of the cut portion of the base portion.
 8. The tuning forkresonator according to claim 5, wherein: a groove, a groove electrodeformed in the groove and a side surface electrode are formed in thefirst and second resonating arms.
 9. The tuning fork resonator elementaccording to claim 1, wherein the width direction of the base issubstantially perpendicular to the longitudinal axis of the first andsecond resonating arms.
 10. The tuning fork resonator element accordingto claim 5, wherein the width direction of the base is substantiallyperpendicular to the longitudinal axis of the first and secondresonating arms.